Metallate electrodes

ABSTRACT

The invention relates to electrodes that contain active materials of the formula: AaMbXxOy wherein A is one or more alkali metals selected from lithium, sodium and potassium; M is selected from one or more transition metals and/or one or more non-transition metals and/or one or more metalloids; X comprises one or more atoms selected from niobium, antimony, tellurium, tantalum, bismuth and selenium; and further wherein 0&lt;a≤6; b is in the range: 0&lt;b≤4; x is in the range 0&lt;x≤1 and y is in the range 2≤y≤10. Such electrodes are useful in, for example, sodium and/or lithium ion battery applications.

FIELD OF THE INVENTION

The present invention relates to electrodes that contain an activematerial comprising a metallate group, and to the use of suchelectrodes, for example in sodium and lithium ion battery applications.The invention also relates to certain novel materials and to the use ofthese materials, for example as an electrode material.

BACKGROUND OF THE INVENTION

Sodium-ion batteries are analogous in many ways to the lithium-ionbatteries that are in common use today; they are both reusable secondarybatteries that comprise an anode (negative electrode), a cathode(positive electrode) and an electrolyte material, both are capable ofstoring power in a compact system by accumulating energy in the chemicalbonds of the cathode, and they both charge and discharge via a similarreaction mechanism. When a sodium-ion (or lithium-ion battery) ischarging, Na⁺ (or Li⁺) ions de-intercalate and migrate towards theanode. Meanwhile charge balancing electrons pass from the cathodethrough the external circuit containing the charger and into the anodeof the battery. During discharge the same process occurs but in theopposite direction. Once a circuit is completed electrons pass back fromthe anode to the cathode and the Na⁺ (or Li⁺) ions travel back to theanode.

Lithium-ion battery technology has enjoyed a lot of attention in recentyears and provides the preferred portable battery for most electronicdevices in use today; however lithium is not a cheap metal to source andis too expensive for use in large scale applications. By contrastsodium-ion battery technology is still in its relative infancy but isseen as advantageous; sodium is much more abundant than lithium andresearchers predict this will provide a cheaper and more durable way tostore energy into the future, particularly for large scale applicationssuch as storing energy on the electrical grid. Nevertheless a lot ofwork has yet to be done before sodium-ion batteries are a commercialreality.

From the prior art, for example in the Journal of Solid State Chemistry180 (2007) 1060-1067, L. Viciu et al disclosed the synthesis, structureand basic magnetic properties of Na₂Co₂TeO₆ and Na₃Co₂SbO₆. Also inDalton Trans 2012, 41, 572, Elena A. Zvereva et al disclosed thepreparation, crystal structure and magnetic properties of Li₃Ni₂SbO₆.Neither of these documents discusses the use of such compounds aselectrode materials in sodium- or lithium-ion batteries.

In a first aspect, the present invention aims to provide a costeffective electrode that contains an active material that isstraightforward to manufacture and easy to handle and store. A furtherobject of the present invention is to provide an electrode that has ahigh initial charge capacity and which is capable of being rechargedmultiple times without significant loss in charge capacity.

Therefore, the present invention provides an electrode that contains anactive material of the formula:A_(a)M_(b)X_(x)O_(y)

-   -   wherein    -   A is one or more alkali metals selected from lithium, sodium and        potassium;    -   M is selected from one or more transition metals and/or one or        more non-transition metals and/or one or more metalloids;    -   X comprises one or more atoms selected from niobium, antimony,        tellurium, tantalum, bismuth and selenium;    -   and further wherein    -   0<a≤6; b is in the range: 0<b≤4; x is in the range 0<x≤1 and y        is in the range 2≤y≤10.

In a preferred embodiment of an electrode of the above formula, one ormore of a, b, x and y are integers, i.e. whole numbers. In analternative embodiment, one or more of a, b, x and y are non-integers,i.e. fractions.

Preferably M comprises one or more transition metals and/or one or morenon-transition metals and/or one or more metalloids selected fromtitanium, vanadium, chromium, molybdenum, tungsten, manganese, iron,osmium, cobalt, nickel, palladium, platinum, copper, silver, gold, zinc,cadmium, magnesium, calcium, beryllium, strontium, barium, aluminium andboron, and particularly preferred is an electrode containing an activematerial wherein M is selected from one or more of copper, nickel,cobalt, manganese, titanium, aluminium, vanadium, magnesium and iron.

The term “metalloids” as used herein is intended to refer to elementswhich have both metal and non-metal characteristics, for example boron.

We have found it advantageous that the electrode contains an activematerial wherein at least one of the one or more transition metals hasan oxidation state of +2 and at least one of the one or morenon-transition metals has an oxidation state of +2.

Other suitable electrodes contain an active material wherein at leastone of the one or more transition metals has an oxidation state ofeither +2 or +3 and at least one of the one or more non-transitionmetals has an oxidation state of +3.

Preferred electrodes contain an active material of the formula:A_(a)M_(b)Sb_(x)O_(y), wherein A is one or more alkali metals selectedfrom lithium, sodium and potassium and M is one or more metals selectedfrom cobalt, nickel, manganese, titanium, iron, copper, aluminium,vanadium and magnesium.

Alternative preferred electrodes contain an active material of theformula: A_(a)M_(b)Te_(x)O_(y), wherein A is one or more alkali metalsselected from lithium, sodium and potassium and M is one or more metalsselected from cobalt, nickel, manganese, titanium, iron, copper,aluminium, vanadium and magnesium.

As described above it is typical that a may be in the range 0<a≤6; b maybe in the range: 0<b≤4; x may be in the range 0<x≤1 and y may be in therange 2≤y≤10. Preferably, however, a may be in the range 0<a≤5; b may bein the range 0≤b≤3; 0.5≤x≤1; and y may be in the range 2≤y≤9.Alternatively, a may be in the range 0<a≤5; b may be in the range 0<b≤2;x may be in the range 0<x≤1; and 2≤y≤8. As mentioned above, one or moreof a, b, x and y may be integers or non-integers.

Extremely beneficial electrochemical results are expected for electrodesthat contain one or more active materials: Na₃Ni₂SbO₆,Na₃Ni_(1.5)Mg_(0.5)SbO₆, Na₃Co₂SbO₆, Na₃Co_(1.5)Mg_(0.5)SbO₆,Na₃Mn₂SbO₆, Na₃Fe₂SbO₆, Na₃Cu₂SbO₆, Na₂AlMnSbO₆, Na₂AlNiSbO₆,Na₂VMgSbO₆, NaCoSbO₄, NaNiSbO₄, NaMnSbO₄, Na₄FeSbO₆,Na_(0.8)CO_(0.6)Sb_(0.4)O₂, Na_(0.8)Ni_(0.6)Sb_(0.4)O₄, Na₂Ni₂TeO₆,Na₂Co₂TeO₆, Na₂Mn₂TeO₆, Na₂Fe₂TeO₆, Na₃Ni_(2-z)Mg_(z)SbO₆ (0≤z≤0.75),Li₃Ni_(1.5)Mg_(0.5)SbO₆, Li₃Ni₂SbO₆, Li₃Mn₂SbO₆, Li₃Fe₂SbO₆,Li₃Ni_(1.5)Mg_(0.5)SbO₆, Li₃Cu₂SbO₆, Li₃Co₂SbO₆, Li₂Co₂TeO₆, Li₂Ni₂TeO₆,Li₂Mn₂TeO₆, LiCoSbO₄, LiNiSba_(t), LiMnSbO₄, Li₃CuSbO₅, Na₄NiTeO₆,Na₂NiSbO₅, Li₂NiSbO₅, Na₄Fe₃SbO₉, Li₄Fe₃SbO₉, Na₂Fe₃SbO₈, Na₅NiSbO₆,Li₅NiSbO₆, Na₄MnSbO₆, Li₄MnSbO₆, Na₃MnTeO₆, Li₃MnTeO₆, Na₃FeTeO₆,Li₃FeTeO₆, Na₄Fe_(1-z)(Ni_(0.5)Ti_(0.5))_(z)SbO₆ (0≤z≤1),Na₄Fe_(0.5)Ni_(0.25)Ti_(0.25)SbO₆,Li₄Fe_(1-z)(Ni_(0.51)Ti_(0.5))_(z)SbO₆ (0≤z≤1),Li₄Fe_(0.5)Ni_(0.25)Ti_(0.25)SbO₆, Na₄Fe_(1-z)(Ni_(0.5)Mn_(0.5))_(z)SbO₆(0≤z≤1), Na₄Fe_(0.5)Ni_(0.25)Mn_(0.25))_(z)SbO₆,Li₄Fe_(1-z)(Ni_(0.5)Mn_(0.5))_(z)SbO₆ (0≤z≤1),Li₄Fe_(0.5)Ni_(0.25)Mn_(0.25)SbO₆, Na_(5-z)Ni_(1-z)Fe_(z)SbO₆ (0≤z≤1),Na_(4.5)Ni_(0.5)Fe_(0.5)SbO₆, Li_(5-z)Ni_(1-z)Fe_(z)SbO₆ (0≤z≤1),Li_(4.5)Ni_(0.5)Fe_(0.5)SbO₆, Na₃Ni_(1.75)Zn_(0.25)SbO₆,Na₃Ni_(1.75)Cu_(0.25)SbO₆, Na₃Ni_(1.50)Mn_(0.50)SbO₆, Li₄FeSbO₆ andLi₄NiTeO₆.

It is convenient to use an electrode according to the present inventionin an energy storage device, particularly an energy storage device foruse as one or more of the following: a sodium and/or lithium ion and/orpotassium cell, a sodium and/or lithium and/or potassium metal ion cell,a non-aqueous electrolyte sodium and/or lithium and/or potassium ioncell, an aqueous electrolyte sodium and/or lithium and/or potassium ioncell.

Electrodes according to the present invention are suitable for use inmany different applications, for example energy storage devices,rechargeable batteries, electrochemical devices and electrochromicdevices.

Advantageously, the electrodes according to the invention are used inconjunction with a counter electrode and one or more electrolytematerials. The electrolyte materials may be any conventional or knownmaterials and may comprise either aqueous electrolyte(s) or non-aqueouselectrolyte(s) or mixtures thereof.

In a second aspect, the present invention provides a novel material ofthe formula: A₃Ni_(2-z)Mg_(z)SbO₆, wherein A is one or more alkalimetals selected from lithium, sodium and potassium and z is in the range0<z<2.

In a third aspect, the present invention provides a novel material ofthe formula: Na₃Mn₂SbO₆.

In a third aspect, the present invention provides a novel material ofthe formula: Na₃Fe₂SbO₆.

The active materials of the present invention may be prepared using anyknown and/or convenient method. For example, the precursor materials maybe heated in a furnace so as to facilitate a solid state reactionprocess. Further, the conversion of a sodium-ion rich material to alithium-ion rich material may be effected using an ion exchange process.

Typical ways to achieve Na to Li ion exchange include:

1. Mixing the sodium-ion rich material with an excess of a lithium-ionmaterial e.g. LiNO₃, heating to above the melting point of LiNO₃ (264°C.), cooling and then washing to remove the excess LiNO₃;

2. Treating the Na-ion rich material with an aqueous solution of lithiumsalts, for example 1M LiCl in water; and

3. Treating the Na-ion rich material with a non-aqueous solution oflithium salts, for example LiBr in one or more aliphatic alcohols suchas hexanol, propanol etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to thefollowing drawings in which:

FIG. 1A is the XRD of Na₃Ni₂SbO₆ prepared according to Example 1;

FIG. 1B shows the Constant current cycling (Cell Voltage versusCumulative Cathode Specific Capacity) of a Na-ion cell: HardCarbon//Na₃Ni₂SbO₆ prepared according to Example 1;

FIG. 2 is the XRD for Na₃Co₂SbO₆ prepared according to Example 2;

FIG. 3 is the XRD for Na₃Mn₂SbO₆ prepared according to Example 3;

FIG. 4A is the XRD for Li₃Cu₂SbO₆ prepared according to Example 22;

FIG. 4B shows Constant current cycling (Electrode Potential versusCumulative Specific Capacity) of Li₃Cu₂SbO₆ prepared according toExample 22;

FIG. 5A is the XRD of Na₂Ni₂TeO₆ prepared according to Example 28;

FIG. 5B shows the Constant current cycling (Electrode Potential versusCumulative Specific Capacity) of Na₂Ni₂TeO₆ prepared according toExample 28;

FIG. 6A is the XRD of Li₃Ni₂SbO₆ prepared according to Example 19;

FIG. 6B shows the Constant current cycling (Electrode Potential versusCumulative Specific Capacity) of Li₃Ni₂SbO₆ prepared according toExample 19;

FIG. 7A is the XRD of Na₃Ni_(2-z)Mg_(z)SbO₆, where z=0.00, 0.25, 0.5,and 0.75, prepared according to method of Examples 34a, 34b, 34c, 34drespectively;

FIG. 7B shows the Constant current cycling (Cell Voltage versusCumulative Cathode Specific Capacity) of a Na-ion cell: HardCarbon//Na₃Ni_(1.5)Mg_(0.5)SbO₆ prepared according to Example 34c;

FIG. 8A is the XRD of Li₃Ni_(1.5)Mg_(0.5)SbO₆ prepared according toExample 17;

FIG. 8B shows the Constant current cycling (Cell Voltage versusCumulative Cathode Specific Capacity) of a Li-ion cell:Graphite//Li₃Ni_(1.5)Mg_(0.5)SbO₆ prepared according to Example 17;

FIG. 9A is the XRD of Na₃Ni_(1.75)Zn_(0.25)SbO₆ prepared according toExample 35;

FIG. 9B shows the long term Constant current cycling performance(cathode specific capacity versus cycle number) of a Na-ion Cellcomprising Carbotron (Kureha Inc.) HardCarbon//Na₃Ni_(1.75)Zn_(0.25)SbO₆ prepared according to Example 35;

FIG. 10A is the XRD of Na₃Ni_(1.75)Cu_(0.25)SbO₆ prepared according toExample 36;

FIG. 10B shows the long term constant current cycling performance(cathode specific capacity versus cycle number) of a Na-ion Cellcomprising: Hard Carbon//Na₃Ni_(1.75)Cu_(0.25)SbO₆ prepared according toExample 36;

FIG. 11A is the XRD of Na₃Ni_(1.25)Mg_(0.75)SbO₆ prepared according toExample 34d;

FIG. 11B shows the long term constant current cycling performance(cathode specific capacity versus cycle number) of a Na-ion Cellcomprising: Hard Carbon//Na₃Ni_(1.25)Mg_(0.75)SbO₆ prepared according toExample 34d;

FIG. 12A is the XRD of Na₃Ni_(1.50)Mn_(0.50)SbO₆ prepared according toExample 37;

FIG. 12B shows the long term constant current cycling performance(cathode specific capacity versus cycle number) of a Na-ion Cellcomprising: Hard Carbon//Na₃Ni_(1.50)Mn_(0.50)SbO₆ prepared according toExample 37;

FIG. 13A is the XRD of Li₄FeSbO₆ prepared according to Example 38;

FIG. 13B shows the constant current cycling data for the Li₄FeSbO₆active material prepared according to Example 38;

FIG. 14A is the XRD of Li₄NiTeO₆ prepared according to Example 39;

FIG. 14B shows the constant current cycling data for the Li₄NiTeO₆active material prepared according to Example 39; and

FIG. 15A is the XRD of Na₄NiTeO₆ prepared according to Example 40; and

FIG. 15B shows the constant current cycling data for the Na₄NiTeO₆prepared according to Example 40.

DETAILED DESCRIPTION

Active materials used in the present invention are prepared on alaboratory scale using the following generic method:

Generic Synthesis Method:

The required amounts of the precursor materials are intimately mixedtogether. The resulting mixture is then heated in a tube furnace or achamber furnace using either a flowing inert atmosphere (e.g. argon ornitrogen) or an ambient air atmosphere, at a furnace temperature ofbetween 400° C. and 1200° C. until reaction product forms. When cool,the reaction product is removed from the furnace and ground into apowder.

Using the above method, active materials used in the present inventionwere prepared as summarised below in Examples 1 to 40

TARGET COMPOUND STARTING FURNACE EXAMPLE (ID code) MATERIALS CONDITIONS 1 Na₃Ni₂SbO₆ Na₂CO₃ Air/800° C., dwell time (X0328) NiCO₃ of 8 hours.Sb₂O₃  2 Na₃Co₂SbO₆ Na₂CO₃ Air/800° C., dwell time (X0325) CoCO₃ of 8hours. Sb₂O₃  3 Na₃Mn₂SbO₆ Na₂CO₃ N₂/800° C., dwell time (X0276) MnCO₃of 8 hours. Sb₂O₃  4 Na₃Fe₂SbO₆ Na₂CO₃ N₂/800° C., dwell time (X0240)Fe₂O₃ of 8 hours. Sb₂O₃  5 Na₃Cu₂SbO₆ Na₂CO₃ Air/800° C., dwell time(X0247) CuO of 8 hours Sb₂O₃  6 Na₂AlMnSbO₆ Na₂CO₃ Air/800° C., dwelltime (X0232) Al(OH)₃ of 8 hours MnCO₃ Sb₂O₃  7 Na₂AlNiSbO₆ Na₂CO₃Air/800° C., dwell time (X0233) Al(OH)₃ of 8 hours NiCO₃ Sb₂O₃  8Na₂VMgSbO₆ Na₂CO₃ N₂/800° C., dwell time (X0245) V₂O₃ of 8 hours Mg(OH)₂NaSbO₃•3H₂O  9 NaCoSbO₄ Na₂CO₃ Air/800° C., dwell time (X0253) CoCO₃ of8 hours Sb₂O₃•3H₂O 10 NaNiSbO₄ Na₂CO₃, Air/800° C., dwell time (X0254)NiCO_(3,) of 8 hours Sb₂O₃ 11 NaMnSbO₄ Na₂CO₃, Air/800° C., dwell time(X0257) MnCO_(3,) of 8 hours Sb₂O₃ 12 Na₄FeSbO₆ Na₂CO₃ Air/800° C.,dwell time (X0260) Fe₂O₃ of 8 hours Sb₂O₃ 13 Na_(0.8)Co_(0.6)Sb_(0.4)O₂Na₂CO₃ Air/800° C., dwell time (X0263) CoCO₃ of 8 hours Sb₂O₃ 14Na_(0.8)Ni_(0.6)Sb_(0.4)O₄ Na₂CO₃ Air/800° C., dwell time (X0264) NiCO₃of 8 hours Sb₂O₃ 15 Na₃Ni_(1.5)Mg_(0.5)SbO₆ Na₂CO₃ Air/800° C., dwelltime (X0336) NiCO₃ of 14 hours Sb₂O₃ Mg(OH)₂ 16 Na₃Co_(1.5)Mg_(0.5)SbO₆Na₂CO₃ Air/800° C., dwell time (X0331) CoCO₃ of 14 hours Sb₂O₃ Mg(OH)₂17 Li₃Ni_(1.5)Mg_(0.5)SbO₆ Li₂CO₃ Air/800° C., dwell time (X0368) NiCO₃of 8 hours Sb₂O₃ Mg(OH)₂ 18 Li₃Co₂SbO₆ Na₂CO₃ Air/800° C., dwell time(X0222) CoCO₃ of 8 hours Sb₂O₃ 19 Li₃Ni₂SbO₆ Na₂CO₃ Air/800° C., dwelltime (X0223) NiCO₃ of 8 hours Sb₂O₃ 20 Li₃Mn₂SbO₆ Na₂CO₃ Air/800° C.,dwell time (X0239) MnCO₃ of 8 hours Sb₂O₃ 21 Li₃Fe₂SbO₆ Li₂CO₃ N2/800°C., dwell time (X0241) Fe₂O₃ of 8 hours Sb₂O₃ 22 Li₃Cu₂SbO₆ Li₂CO₃Air/800° C.,dwell time (X0303) CuO of 8 hours Sb₂O₃ 23 LiCoSbO₄ Li₂CO₃Air/800° C., dwell time (X0251) CoO₃ of 8 hours Sb₂O₃ 24 LiNiSbO₄ Li₂CO₃Air/800° C., dwell time (X0252) NiCO₃ of 8 hours Sb₂O₃ 25 LiMnSbO₄Li₂CO₃ Air/800° C., dwell time (X0256) MnCO₃ of 8 hours Sb₂O₃ 26Li₃CuSbO₅ Li₂CO₃ Air/800° C., dwell time (X0255) CuO of 8 hours Sb₂O₃ 27Na₂Co₂TeO₆ Na₂CO₃ Air/800° C., dwell time (X0216) CoCO₃ of 8 hours TeO₂28 Na₂Ni₂TeO₆ Na₂CO₃ Air/800° C., dwell time (X0217) NiCO₃ of 8 hoursTeO₂ 29 Na₂Mn₂TeO₆ Na₂CO₃ Air/800° C. (X0234) MnCO₃ TeO₂ 30 Na₂Fe₂TeO₆Na₂CO₃ N₂/800° C., dwell time (X0236) Fe₂O₃ of 8 hours TeO₂ 31Li₂Co₂TeO₆ Li₂CO₃ Air/800° C., dwell time (X0218) CoCO₃ of 8 hours TeO₂32 Li₂Ni₂TeO₆ Li₂CO₃ Air/800° C., dwell (X0219) NiCO₃ time of 8 hoursTeO₂ 33 Li₂Mn₂TeO₆ Li₂CO₃ Air/800° C., dwell time (X0235) MnCO₃ of 8hours TeO₂ 34 Na₃Ni_(2−z)Mg_(z)SbO₆ Na₂CO₃ Air/800° C., dwell time 34a Z= 0.00 (X0221) = E.g. 1 NiCO₃ of 8-14 hours 34b Z = 0.25 (X0372) Mg(OH)₂34c Z = 0.5 (X0336) = E.g. 15 Sb₂O₃ 34d Z = 0.75 (X0373) 35Na₃Ni_(1.75)Zn_(0.25)SbO₆ Na₂CO₃, NiCO₃, Air/800° C., dwell (X0392)Sb₂O₃, ZnO time of 8 hours 36 Na₃Ni_(1.75)Cu_(0.25)SbO₆ Na₂CO₃, NiCO₃,Air/800° C., dwell (X0393) Sb₂O₃, CuO time of 8 hours 37Na₃Ni_(1.50)Mn_(0.50)SbO₆ Na₂CO₃, NiCO₃, Air/800° C., dwell (X0380)Sb₂O₃, MnO₂ time of 8 hours 38 Li₄FeSbO₆ Li₂CO₃, Fe₂O₃, Air/800° C.,dwell (X1120A) Sb₂O₃ time of 8 hours followed by 800° C., for a further8 hours 39 Li₄NiTeO₆ Li₂CO₃, NiCO₃, Air/800° C., dwell (X1121) TeO₂ timeof 8 hours 40 Na₄NiTeO₆ Na₂CO₃, NiCO₃, Air/800° C., dwell (X1122) TeO₂time of 8 hours

Product Analysis Using XRD

All of the product materials were analysed by X-ray diffractiontechniques using a Siemens D5000 powder diffractometer to confirm thatthe desired target materials had been prepared and to establish thephase purity of the product material and to determine the types ofimpurities present. From this information it is possible to determinethe unit cell lattice parameters.

The general operating conditions used to obtain the XRD spectra are asfollows:

Slits sizes: 1 mm, 1 mm, 0.1 mm

Range: 20=5°-60°

X-ray Wavelength=1.5418 Å) (Cu Kα)

Speed: 0.5 or 1.0 second/step

Increment: 0.015° or 0.025°

Electrochemical Results

The target materials were tested in a lithium metal anode testelectrochemical cell to determine their specific capacity and also toestablish whether they have the potential to undergo charge anddischarge cycles. A lithium metal anode test electrochemical cellcontaining the active material is constructed as follows:

Generic Procedure to Make a Lithium Metal Test Electrochemical Cell

The positive electrode is prepared by solvent-casting a slurry of theactive material, conductive carbon, binder and solvent. The conductivecarbon used is Super P (Timcal). PVdF co-polymer (e.g. Kynar Flex 2801,Elf Atochem Inc.) is used as the binder, and acetone is employed as thesolvent. The slurry is then cast onto glass and a free-standingelectrode film is formed as the solvent evaporates. The electrode isthen dried further at about 80° C. The electrode film contains thefollowing components, expressed in percent by weight: 80% activematerial, 8% Super P carbon, and 12% Kynar 2801 binder. Optionally, analuminium current collector may be used to contact the positiveelectrode. Metallic lithium on a copper current collector may beemployed as the negative electrode. The electrolyte comprises one of thefollowing: (i) a 1 M solution of LiPF₆ in ethylene carbonate (EC) anddimethyl carbonate (DMC) in a weight ratio of 1:1; (ii) a 1 M solutionof LiPF₆ in ethylene carbonate (EC) and diethyl carbonate (DEC) in aweight ratio of 1:1; or (iii) a 1 M solution of LiPF₆ in propylenecarbonate (PC) A glass fibre separator (Whatman, GF/A) or a porouspolypropylene separator (e.g. Celgard 2400) wetted by the electrolyte isinterposed between the positive and negative electrodes.

Generic Procedure to Make a Hard Carbon Na-Ion Cell

The positive electrode is prepared by solvent-casting a slurry of theactive material, conductive carbon, binder and solvent. The conductivecarbon used is Super P (Timcal). PVdF co-polymer (e.g. Kynar Flex 2801,Elf Atochem Inc.) is used as the binder, and acetone is employed as thesolvent. The slurry is then cast onto glass and a free-standingelectrode film is formed as the solvent evaporates. The electrode isthen dried further at about 80° C. The electrode film contains thefollowing components, expressed in percent by weight: 80% activematerial, 8% Super P carbon, and 12% Kynar 2801 binder. Optionally, analuminium current collector may be used to contact the positiveelectrode.

The negative electrode is prepared by solvent-casting a slurry of thehard carbon active material (Carbotron P/J, supplied by Kureha),conductive carbon, binder and solvent. The conductive carbon used isSuper P (Timcal). PVdF co-polymer (e.g. Kynar Flex 2801, Elf AtochemInc.) is used as the binder, and acetone is employed as the solvent. Theslurry is then cast onto glass and a free-standing electrode film isformed as the solvent evaporates. The electrode is then dried further atabout 80° C. The electrode film contains the following components,expressed in percent by weight: 84% active material, 4% Super P carbon,and 12% Kynar 2801 binder. Optionally, a copper current collector may beused to contact the negative electrode.

Generic Procedure to Make a Graphite Li-Ion Cell

The positive electrode is prepared by solvent-casting a slurry of theactive material, conductive carbon, binder and solvent. The conductivecarbon used is Super P (Timcal). PVdF co-polymer (e.g. Kynar Flex 2801,Elf Atochem Inc.) is used as the binder, and acetone is employed as thesolvent. The slurry is then cast onto glass and a free-standingelectrode film is formed as the solvent evaporates. The electrode isthen dried further at about 80° C. The electrode film contains thefollowing components, expressed in percent by weight: 80% activematerial, 8% Super P carbon, and 12% Kynar 2801 binder. Optionally, analuminium current collector may be used to contact the positiveelectrode.

The negative electrode is prepared by solvent-casting a slurry of thegraphite active material (Crystalline Graphite, supplied by ConocoInc.), conductive carbon, binder and solvent. The conductive carbon usedis Super P (Timcal). PVdF co-polymer (e.g. Kynar Flex 2801, Elf AtochemInc.) is used as the binder, and acetone is employed as the solvent. Theslurry is then cast onto glass and a free-standing electrode film isformed as the solvent evaporates. The electrode is then dried further atabout 80° C. The electrode film contains the following components,expressed in percent by weight: 92% active material, 2% Super P carbon,and 6% Kynar 2801 binder. Optionally, a copper current collector may beused to contact the negative electrode.

Cell Testing

The cells are tested as follows using Constant Current Cyclingtechniques.

The cell is cycled at a given current density between pre-set voltagelimits. A commercial battery cycler from Maccor Inc. (Tulsa, Okla., USA)is used. On charge, sodium (lithium) ions are extracted from the activematerial. During discharge, sodium (lithium) ions are re-inserted intothe active material.

Results:

Na₃Ni₂SbO₆ Prepared According to Example 1.

Referring to FIG. 1B. The Cell #202071 shows the constant currentcycling data for the Na₃Ni₂SbO₆ active material (X0328) made accordingto Example 1 in a Na-ion cell where it is coupled with a Hard Carbon(Carbotron P/J) anode material. The electrolyte used a 0.5 M solution ofNaClO₄ in propylene carbonate. The constant current data were collectedat an approximate current density of 0.05 mA/cm² between voltage limitsof 1.80 and 4.00 V. To fully charge the cell the Na-ion cell waspotentiostatically held at 4.0 V at the end of the constant currentcharging process. The testing was carried out at room temperature. It isshown that sodium ions are extracted from the cathode active material,Na₃Ni₂SbO₆, and inserted into the Hard Carbon anode during the initialcharging of the cell. During the subsequent discharge process, sodiumions are extracted from the Hard Carbon and re-inserted into theNa₃Ni₂SbO₆ cathode active material. The first discharge processcorresponds to a specific capacity for the cathode of 86 mAh/g,indicating the reversibility of the sodium ion extraction-insertionprocesses. The generally symmetrical nature of the charge-dischargecurves further indicates the excellent reversibility of the system, andthe low level of voltage hysteresis (i.e. the voltage difference betweenthe charge and discharge processes) is extremely small, and this alsoindicates the excellent kinetics of the extraction-insertion reactions.This is an important property that is useful for producing a high rateactive material.

Na₃Cu₂SbO₆ Prepared According to Example 22.

Referring to FIG. 4B. The Cell #202014 shows the constant currentcycling data for the Li₃Cu₂SbO₆ active material (X0303) made accordingto Example 22. The electrolyte used a 1.0 M solution of LiPF₆ inethylene carbonate (EC) and diethyl carbonate (DEC). The constantcurrent data were collected using a lithium metal counter electrode atan approximate current density of 0.02 mA/cm² between voltage limits of3.00 and 4.20 V. The upper voltage limit was increased by 0.1 V onsubsequent cycles. The testing was carried out at room temperature. Itis shown that lithium ions are extracted from the active material duringthe initial charging of the cell. A charge equivalent to a materialspecific capacity of 33 mAh/g is extracted from the active material. There-insertion process corresponds to 14 mAh/g, indicating thereversibility of the ion extraction-insertion processes. The generallysymmetrical nature of the charge-discharge curves further indicates theexcellent reversibility of the system. In addition, the level of voltagehysteresis (i.e. the voltage difference between the charge and dischargeprocesses) is extremely small, indicating the excellent kinetics of theextraction-insertion reactions. This is an important property that isuseful for producing a high rate active material.

Na₂Ni₂TeO₆ Prepared According to Example 28.

Referring to FIG. 5B. The Cell #201017 shows the constant currentcycling data for the Na₂Ni₂TeO₆ active material (X0217) made accordingto Example 28. The electrolyte used a 0.5 M solution of NaClO₄ inpropylene carbonate. The constant current data were collected using alithium metal counter electrode at an approximate current density of0.02 mA/cm² between voltage limits of 3.00 and 4.20 V. The upper voltagelimit was increased by 0.1 V on subsequent cycles. The testing wascarried out at room temperature. It is shown that sodium ions areextracted from the active material during the initial charging of thecell. A charge equivalent to a material specific capacity of 51 mAh/g isextracted from the active material.

It is expected from thermodynamic considerations that the sodiumextracted from the Na₂Ni₂TeO₆ active material during the initialcharging process, enters the electrolyte, and would then be displacement‘plated’ onto the lithium metal anode (i.e. releasing more lithium intothe electrolyte). Therefore, during the subsequent discharging of thecell, it is assumed that a mix of lithium and sodium ions is re-insertedinto the active material. The re-insertion process corresponds to 43mAh/g; indicating the reversibility of the ion extraction-insertionprocesses. The generally symmetrical nature of the charge-dischargecurves further indicates the excellent reversibility of the system. Inaddition, the level of voltage hysteresis (i.e. the voltage differencebetween the charge and discharge processes) is extremely small,indicating the excellent kinetics of the extraction-insertion reactions.This is an important property that is useful for producing a high rateactive material.

Li₃Ni₂SbO₆ Prepared According to Example 19.

Referring to FIG. 6B. The Cell #201020 shows the constant currentcycling data for the Li₃Ni₂SbO₆ active material (X0223) made followingExample 19. The electrolyte used a 1.0 M solution of LiPF₆ in ethylenecarbonate (EC) and diethyl carbonate (DEC). The constant current datawere collected using a lithium metal counter electrode at an approximatecurrent density of 0.02 mA/cm², between voltage limits of 3.00 and 4.20V. The upper voltage limit was increased by 0.1 V on subsequent cycles.The testing was carried out at room temperature. It is shown thatlithium ions are extracted from the active material during the initialcharging of the cell. A charge equivalent to a material specificcapacity of 130 mAh/g is extracted from the active material. There-insertion process corresponds to 63 mAh/g and indicates thereversibility of the ion extraction-insertion processes. The generallysymmetrical nature of the charge-discharge curves further indicates theexcellent reversibility of the system. In addition, the level of voltagehysteresis (i.e. the voltage difference between the charge and dischargeprocesses) is extremely small, indicating the excellent kinetics of theextraction-insertion reactions. This is an important property that isuseful for producing a high rate active material.

Na₃Ni_(1.5)Mg_(0.5)SbO₆ Prepared According to Example 34C.

Referring to FIG. 7B. The Cell #203016 shows the constant currentcycling data for the Na₃Ni_(1.5)Mg_(0.5)SbO₆ active material (X0336)made following Example 34c in a Na-ion cell where it is coupled with aHard Carbon (Carbotron P/J) anode material. The electrolyte used a 0.5 Msolution of NaClO₄ in propylene carbonate. The constant current datawere collected at an approximate current density of 0.05 mA/cm² betweenvoltage limits of 1.80 and 4.20 V.

To fully charge the cell the Na-ion cell was potentiostatically held at4.2 V at the end of the constant current charging process. The testingwas carried out at room temperature. It is shown that sodium ions areextracted from the cathode active material, Na₃Ni_(1.6)Mg_(0.6)SbO₆, andinserted into the Hard Carbon anode during the initial charging of thecell. During the subsequent discharge process, sodium ions are extractedfrom the Hard Carbon and re-inserted into the Na₃Ni_(1.6)Mg_(0.5)SbO₆cathode active material. The first discharge process corresponds to aspecific capacity for the cathode of 91 mAh/g, indicating thereversibility of the sodium ion extraction-insertion processes. Thegenerally symmetrical nature of the charge-discharge curves furtherindicates the excellent reversibility of the system. In addition, thelevel of voltage hysteresis (i.e. the voltage difference between thecharge and discharge processes) is extremely small, indicating theexcellent kinetics of the extraction-insertion reactions. This is animportant property that is useful for producing a high rate activematerial.

Li₃Ni_(1.5)Mg_(0.5)SbO₆ Prepared According to Example 17.

Referring to FIG. 8B. The Cell #203018 shows the constant currentcycling data for the Li₃Ni_(1.6)Mg_(0.5)SbO₆ active material (X0368)made according to Example 17 in a Li-ion cell where it is coupled with aCrystalline Graphite (Conoco Inc.) anode material. The electrolyte useda 1.0 M solution of LiPF₆ in ethylene carbonate (EC) and diethylcarbonate (DEC). The constant current data were collected at anapproximate current density of 0.05 mA/cm² between voltage limits of1.80 and 4.20 V. To fully charge the cell the Li-ion cell waspotentiostatically held at 4.2 V at the end of the constant currentcharging process. The testing was carried out at room temperature. It isshown that lithium ions are extracted from the cathode active material,Li₃Ni_(1.6)Mg_(0.6)SbO₆, and inserted into the Graphite anode during theinitial charging of the cell. During the subsequent discharge process,lithium ions are extracted from the Graphite and re-inserted into theLi₃Ni_(1.6)Mg_(0.6)SbO₆ cathode active material. The first dischargeprocess corresponds to a specific capacity for the cathode of 85 mAh/g,indicating the reversibility of the lithium ion extraction-insertionprocesses. The generally symmetrical nature of the charge-dischargecurves further indicates the excellent reversibility of the system. Inaddition, the level of voltage hysteresis (i.e. the voltage differencebetween the charge and discharge processes) is extremely small,indicating the excellent kinetics of the extraction-insertion reactions.This is an important property that is useful for producing a high rateactive material.

Na₃Ni_(1.76)Zn_(0.26)SbO₆ Prepared According to Example 35.

FIG. 9B (Cell#203054) shows the long term constant current cyclingperformance (cathode specific capacity versus cycle number) of a Na-ionCell comprising Carbotron (Kureha Inc.) HardCarbon//Na₃Ni_(1.75)Zn_(0.25)SbO₆ (Material=X0392) using a 0.5 MNaClO₄-propylene carbonate (PC) electrolyte. The constant currentcycling test was carried out at 25° C. between voltage limits of 1.8 and4.2 V. To fully charge the cell, the Na-ion cell was held at a cellvoltage of 4.2 V at the end of the constant current charging processuntil the cell current had decayed to one tenth of the constant currentvalue. During the charging of the cell, sodium ions are extracted fromthe cathode active material, and inserted into the Hard Carbon anode.During the subsequent discharge process, sodium ions are extracted fromthe Hard Carbon and re-inserted into the cathode active material. Theinitial cathode specific capacity (cycle 1) is 70 mAh/g. The Na-ion cellcycles more than 50 times with low capacity fade.

Na₃Ni_(1.75)Cu_(0.25)SbO₆ Prepared According to Example 36.

FIG. 10B (Cell#203055) shows the long term constant current cyclingperformance (cathode specific capacity versus cycle number) of a Na-ionCell comprising: Hard Carbon//Na₃Ni_(1.75)Cu_(0.25)SbO₆ (Material=X0393)using a 0.5 M NaClO₄-propylene carbonate (PC) electrolyte. The constantcurrent cycling test was carried out at 25° C. between voltage limits of1.8 and 4.2 V. To fully charge the cell, the Na-ion cell was held at acell voltage of 4.2 V at the end of the constant current chargingprocess until the cell current had decayed to one tenth of the constantcurrent value. During the charging of the cell, sodium ions areextracted from the cathode active material, and inserted into the HardCarbon anode. During the subsequent discharge process, sodium ions areextracted from the Hard Carbon and re-inserted into the cathode activematerial. The initial cathode specific capacity (cycle 1) is 62 mAh/g.The Na-ion cell cycles 18 times with low capacity fade.

Na₃Ni_(1.25)Mg_(0.75)SbO₆ Prepared According to Example 34d.

FIG. 11B (Cell#203047) shows the long term constant current cyclingperformance (cathode specific capacity versus cycle number) of a Na-ionCell comprising: Hard Carbon//Na₃Ni_(1.25)Mg_(0.75)SbO₆ (Material=X0373)using a 0.5 M NaClO₄-propylene carbonate (PC) electrolyte. The constantcurrent cycling test was carried out at 25° C. between voltage limits of1.8 and 4.0 V. To fully charge the cell, the Na-ion cell was held at acell voltage of 4.0 V at the end of the constant current chargingprocess until the cell current had decayed to one tenth of the constantcurrent value. During the charging of the cell, sodium ions areextracted from the cathode active material, and inserted into the HardCarbon anode.

During the subsequent discharge process, sodium ions are extracted fromthe Hard Carbon and re-inserted into the cathode active material. Theinitial cathode specific capacity (cycle 1) is 83 mAh/g. The Na-ion cellcycles more than 40 times with low capacity fade.

Na₃Ni_(1.50)Mn_(0.50)SbO₆ Prepared According to Example 37.

FIG. 12B (Cell#203029) shows the long term constant current cyclingperformance (cathode specific capacity versus cycle number) of a Na-ionCell comprising: Hard Carbon//Na₃Ni_(1.50)Mn_(0.50)SbO₆ (Material=X0380)using a 0.5 M NaClO₄-propylene carbonate (PC) electrolyte. The constantcurrent cycling test was carried out at 25° C. between voltage limits of1.8 and 4.2 V. To fully charge the cell, the Na-ion cell was held at acell voltage of 4.2 V at the end of the constant current chargingprocess until the cell current had decayed to one tenth of the constantcurrent value. During the charging of the cell, sodium ions areextracted from the cathode active material, and inserted into the HardCarbon anode. During the subsequent discharge process, sodium ions areextracted from the Hard Carbon and re-inserted into the cathode activematerial. The initial cathode specific capacity (cycle 1) is 78 mAh/g.The Na-ion cell cycles 13 times with low capacity fade.

Li₄FeSbO₆ Prepared According to Example 38.

FIG. 13B (Cell #303017) shows the constant current cycling data for theLi₄FeSbO₆ active material (X1120A). The electrolyte used a 1.0 Msolution of LiPF₆ in ethylene carbonate (EC) and diethyl carbonate(DEC). The constant current data were collected using a lithium metalcounter electrode at an approximate current density of 0.04 mA/cm²between voltage limits of 2.50 and 4.30 V. The testing was carried outat 25° C. It is shown that lithium ions are extracted from the activematerial during the initial charging of the cell. A charge equivalent toa material specific capacity of 165 mAh/g is extracted from the activematerial. The re-insertion process corresponds to 100 mAh/g, indicatingthe reversibility of the ion extraction-insertion processes. Thegenerally symmetrical nature of the charge-discharge curves furtherindicates the excellent reversibility of the system.

Li₄NiTeO₆ Prepared According to Example 39

FIG. 14B (Cell #303018) shows the constant current cycling data for theLi₄NiTeO₆ active material (X1121). The electrolyte used a 1.0 M solutionof LiPF₆ in ethylene carbonate (EC) and diethyl carbonate (DEC). Theconstant current data were collected using a lithium metal counterelectrode at an approximate current density of 0.04 mA/cm² betweenvoltage limits of 2.50 and 4.40 V. The testing was carried out at 25° C.It is shown that lithium ions are extracted from the active materialduring the initial charging of the cell. A charge equivalent to amaterial specific capacity of 168 mAh/g is extracted from the activematerial. The re-insertion process corresponds to 110 mAh/g, indicatingthe reversibility of the alkali ion extraction-insertion processes. Thegenerally symmetrical nature of the charge-discharge curves furtherindicates the excellent reversibility of the system.

Na₄NiTeO₆ Prepared According to Example 40.

FIG. 15B (Cell #303019) shows the constant current cycling data for theNa₄NiTeO₆ active material (X1122). The electrolyte used a 1.0 M solutionof LiPF₆ in ethylene carbonate (EC) and diethyl carbonate (DEC). Theconstant current data were collected using a lithium metal counterelectrode at an approximate current density of 0.04 mA/cm² betweenvoltage limits of 2.50 and 4.30 V. The testing was carried out at 25° C.It is shown that sodium ions are extracted from the active materialduring the initial charging of the cell. A charge equivalent to amaterial specific capacity of 75 mAh/g is extracted from the activematerial. The re-insertion process corresponds to 30 mAh/g, indicatingthe reversibility of the alkali ion extraction-insertion processes. Thegenerally symmetrical nature of the charge-discharge curves furtherindicates the excellent reversibility of the system.

The invention claimed is:
 1. An electrode containing an active materialof the formula:A_(a)M_(b)X_(x)O_(y) wherein A is one or more alkali metals selectedfrom sodium or a mixture of sodium and potassium; M is selected from oneor more transition metals and/or one or more non-transition metalsand/or one or more metalloids; X comprises one or more atoms selectedfrom niobium, antimony, tellurium, tantalum, bismuth and selenium;wherein 0<a≤6; b is in the range: 0<b≤4; x is in the range 0.5≤x≤1 and yis in the range 2≤y≤10 and further wherein M comprises one or moretransition metals and/or one or more non-transition metals and/or one ormore metalloids selected from titanium, vanadium, chromium, molybdenum,tungsten, manganese, iron, osmium, cobalt, nickel, palladium, platinum,copper, silver, gold, zinc, cadmium, magnesium, calcium, beryllium,strontium, barium, aluminium and boron.
 2. The electrode containing anactive material according to claim 1 wherein at least one of the one ormore transition metals has an oxidation state of +2 and at least one ofthe one or more non-transition metals has an oxidation state of +2. 3.The electrode containing an active material according to claim 1 whereinat least one of the one or more transition metals has an oxidation stateof either +2 or +3 and wherein at least one of the one or morenon-transition metals has an oxidation state of +3.
 4. The electrodecontaining an active material according to claim 1 wherein M is selectedfrom one or more of copper, nickel, cobalt, manganese, aluminium,vanadium, magnesium and iron.
 5. The electrode containing an activematerial according to claim 1 of the formula: A_(a)M_(b)X_(x)O_(y),wherein A is one or more alkali metals selected from sodium or a mixtureof sodium and potassium; M is one or more metals selected from cobalt,nickel, manganese, iron, copper, aluminium, vanadium and magnesium; X isone or more selected from antimony and tellurium; a is in the range0<a≤5; b is in the range 0<b≤3; and y is in the range 2≤y≤9.
 6. Anelectrode containing one or more active materials selected from:Na₃Ni₂SbO₆, Na₃Ni_(1.5)Mg_(0.5)SbO₆, Na₃Co₂SbO₆,Na₃Co_(1.5)Mg_(0.5)SbO₆, Na₃Mn₂SbO₆, Na₃Fe₂SbO₆, Na₃Cu₂SbO₆,Na₂AlMnSbO₆, Na₂AlNiSbO₆, Na₂VMgSbO₆, NaCoSbO₄, NaNiSbO₄, NaMnSbO₄,Na₄FeSbO₆, Na_(0.8)Co_(0.6)Sb_(0.4)O₂, Na_(0.8)Ni_(0.6)Sb_(0.4)O₄,Na₂Ni₂TeO₆, Na₂Co₂TeO₆, Na₂Mn₂TeO₆, Na₂Fe₂TeO₆, Na₃Ni_(2-z)Mg_(z)SbO₆(0≤z≤0.75), Na₄NiTeO₆, Na₂NiSbO₅, Na₄Fe₃SbO₉, Na₂Fe₃SbO₈, Na₅NiSbO₆,Na₄MnSbO₆, Na₃MnTeO₆, Na₃FeTeO₆, Na₄Fe_(1-z)(Ni_(0.5)Ti_(0.5))_(z)SbO₆(0≤z≤1), Na₄Fe_(0.5)Ni_(0.25)Ti_(0.25)SbO₆,Na₄Fe_(1-z)(Ni_(0.5)Mn_(0.5))_(z)SbO₆ (0≤z≤1),Na₄Fe_(0.5)Ni_(0.25)Mn_(0.25)SbO₆, Na_(5-z)Ni_(1-z)Fe_(z)SbO₆ (0≤z≤1),Na_(4.5)Ni_(0.5)Fe_(0.5)SbO₆, Na₃Ni_(1.75)Zn_(0.25)SbO₆,Na₃Ni_(1.75)Cu_(0.25)SbO₆ and Na₃Ni_(1.50)Mn_(0.50)SbO₆.
 7. Use of anelectrode according to claim 1 in conjunction with a counter electrodeand one or more electrolyte materials.
 8. Use of an electrode accordingto claim 1 in conjunction with a counter electrode and one or moreelectrolyte materials wherein the electrolyte material comprises one ormore selected from an aqueous electrolyte material and a non-aqueouselectrolyte material.
 9. An energy storage device comprising anelectrode according to claim
 1. 10. A rechargeable battery comprising anelectrode according to claim
 1. 11. An electrochemical device comprisingan electrode according to claim
 1. 12. An electrochromic devicecomprising an electrode according to claim
 1. 13. A rechargeable batterycomprising an energy storage device according to claim j.
 14. Anelectrochemical device comprising energy storage device according toclaim
 9. 15. An electrochromic device comprising energy storage deviceaccording to claim 9.